Additive manufacturing, commonly known as ‘3D printing’, typically involves fabricating an object from successive, planar layers which form cross-sections of the object, responsive to computer instructions derived from a three-dimensional digital model of the object. Popular additive manufacturing techniques include fused deposition modeling (FDM), stereolithography (SLA) and selective laser sintering (SLS); all of which typically involving a ‘printer head’ moving across a gantry system and selectively fabricating material adjacent the printer head, either by selectively depositing molten material, solidifying liquid material or fusing powdered material, thereby fabricating the object.
Regardless of which additive manufacturing process is used, it is typical for each layer of the fabricated object to have a generally consistent, uniform thickness (disregarding imperfections in the surfaces of the layer due to the limitations or inaccuracies of the apparatus used). Also, generally, the thickness of each layer of the object is typically specified by a user or software, prior to fabricating the object, to be equal to all other layers. For example, if it is a priority to fabricate the object as fast as possible, the layer thickness is set to a maximum value, thereby reducing the time required to fabricate the object but resulting in a relatively rough or ‘stepped’ surface finish on the object. Alternatively, if it is a priority to fabricate the object having an accurate geometry and/or fine surface finish (known as printing at ‘high resolution’), the layer thickness is set to a minimum value, thereby reducing roughness/step height and resulting in a smooth surface finish, but increasing the time required to fabricate the object.
In some scenarios, it is known to configure the apparatus to fabricate different portions of the object from different layer thicknesses for structural reasons. For example, when fabricating an object using a selective deposition process, it is known to configure the apparatus to fabricate the initial layers of the object at a 2‘X’ thickness dimension and the remaining layers at an ‘X’ thickness dimension. This ensures that the initial layers have sufficient heat to firmly adhere to a base of the apparatus to prevent the object moving during the remainder of the fabrication process, and/or to provide improved stability for the object during the fabrication process.
Similarly, the apparatus may be configured to fabricate different portions of the object from different layer thicknesses due to the geometry of the portion. For example, where the object comprises a first portion arranged as a cube and a second portion arranged as a domed roof on top of the cube, the apparatus may be configured to fabricate the cube from layers having a 5‘X’ thickness dimension and the domed portion from layers having an ‘X’ thickness dimension. This approach allows the first portion of the object, which comprises vertical walls only, to be fabricated as fast as possible, and the second portion of the object, which comprises curved walls (which are most susceptible to forming a stepped appearance), to be fabricated more slowly, thereby achieving an acceptable surface finish on both portions of the object and minimising build time where possible.
Regardless of which approach is taken, objects fabricated in successive layers as described above often suffer from a number of problems. For example, as each layer is generally parallel to each other and planar, the bond between adjacent layers is relatively weak. This can mean that when the object is exposed to certain environmental conditions (e.g. exposure to temperature variation, dust, chemicals and/or moisture) or mechanical stresses, the bond between layers can degrade and the layers delaminate from each other. This is can be fatal to the functionality of the object. Furthermore, the geometry of the object able to be fabricated in successive, planar layers is inherently limited, meaning that some geometries cannot be fabricated or may require additional support structures to be constructed to support the object during the fabrication process, increasing the complexity of the process, time required and cost.
Accordingly, it would be useful to provide an alternative method of fabricating an object with an additive manufacturing process which provides an improved bond between fabricated layers or otherwise reduces the problems associated with fabricated objects delaminating. Furthermore, it would be useful to provide a solution that avoids or ameliorates any of the disadvantages present in the prior art, or which provides another alternative to the prior art approaches.